System identification issues in multirate systems

Discusses system identification of multirate systems. In particular, the practically useful case of systems with fast manipulative variable sampling and slow output sampling is considered. The lifting method is used to analyze the multirate system in a state-space framework. A subspace identification algorithm, is first used to identify the lifted multirate system. The single-rate model at the faster sampling rate is then extracted from this estimated system, three possible extracting algorithms are also presented. The paper also discusses methods to generate an excitation sequence for identifying multirate systems. Simulation and experiment results are included in the paper.